This invention relates to earth boring and more particularly to roller reamers useful in the drill strings employed in the rotary system of drilling, either immediately above the drill bit or higher up in the string, i.e., between drill collars, for maintaining the hole at full gage.
Conventional roller reamers employ a plurality of rollers rotatably mounted at the periphery of the reamer body. The reamer body is provided at its ends with threaded connectors for connection at its top to a pipe string which extends back to the drill rig and at its bottom to a drill bit. A discussion of prior art roller reamers, field replaceable rollers, the lubrication of rollers, and mining tools is discussed in U.S. Pat. No. 4,182,425 and is incorporated herein by reference. Summarizing a portion of that discussion, the roller reamers may employ smooth rollers, hard faced rollers, or rollers with milled teeth. In overall operation the rotation of the reamer causes the cutters to rotate and to enlarge the borehole produced by the drill bit.
The rollers for reamers are often mounted to rotate on a shaft with the shaft mounted at the periphery of the reamer body. See U.S. Pat. Nos. 2,026,323; 2,189,031; 2,190,350; 2,199,693; 2,218,743; 2,272,405; 3,897,837; 4,013,325; 4,020,910; 4,182,425; 4,226,291; and 4,262,759. Other reamers, such as are disclosed in U.S. Pat. Nos. 4,102,416 and 4,227,586, include bearing journals extending from each end of the roller for providing rotation with respect to the reamer body.
The rollers and shafts are generally mounted at the periphery of the reamer body by blocks received in sockets formed in the body of the reamer such as shown in U.S. Pat. Nos. 2,026,323; 2,189,031; 2,190,350; 2,199,693; 2,218,743; 4,102,416; 4,182,425; 4,227,586; and 4,262,759. Generally, the blocks have bores for receiving the ends of the shaft. Such is shown in U.S. Pat. Nos. 2,026,323; 2,189,031; 2,190,350; 2,199,693; 2,218,743; 2,272,405; 4,182,425; and 4,227,586.
The ends of the shaft are secured to the block of the reamer body by various means. U.S. Pat. Nos. 2,026,323 and 4,182,425 disclose welding the upper end of the shaft to the block. U.S. Pat. No. 2,189,031 discloses threading the ends of the shaft into the blocks. U.S. Pat. Nos. 2,190,350; 2,199,693; 2,218,743; 2,272,405; and 3,897,837 teach holding the shaft in the block through the use of a key or pin. U.S. Pat. Nos. 2,189,031 and 2,218,743 show the use of screws to hold the shaft within the block.
Roller radial bearings and thrust washers have been used between the roller and shaft to facilitate the rotation of the roller thereon. Such bearings are shown in U.S. Pat. Nos. 2,026,323; 2,190,350; 2,199,693; 2,218,743; 2,272,405; 4,020,910; and 4,182,425. Other patents show the use of shaft bushings. U.S. Pat. No. 2,218,743 illustrates a shaft bushing welded to the block. U.S. Pat. Nos. 2,190,350 and 2,199,693 illustrate a bushing welded to the cutter. U.S. Pat. Nos. 2,218,743; 2,272,405; and 4,020,910 disclose shaft bushings with downwardly facing shoulders opposing the upper end of the rollers for the taking of thrust. U.S. Pat. No. 3,897,837 discloses thrust bearings between a shoulder on the shaft and the end of the rollers. U.S. Pat. Nos. 2,026,323; 2,190,350; and 2,199,693 show a bearing race disposed in part in the shaft.
Radially projecting shoulders have been utilized on the shaft and are disclosed in U.S. Pat. Nos. 2,026,323; 2,189,031; 3,897,837; and 4,102,416. In U.S. Pat. Nos. 2,189,031; 3,897,837; and 4,102,416 the shoulder of the shaft extends up inside the block. In U.S. Pat. No. 2,189,031 there appears to be an annular space between the block, shaft shoulder, and the end of the roller.
The space between each roller and shaft may be lubricated by various means. For example, such lubrication may be accomplished by the drilling fluid such as by air, water, mud, and oil passing through the body and back up the earth bore outside the reamer body. Reference may be made to U.S. Pat. Nos. 2,026,323; 2,190,350; 2,189,031; 2,199,693; 2,218,743; 2,272,405; 4,102,416; and 4,226,291. Another means is grease disposed between the roller and shaft. Drill bits have been provided with sealed lubricated bearings which have greatly increased the life of bits. See U.S. Pat. No. 4,249,622. Further, sealed lubricated bearings have not only been used for drill bits but for roller reamers and stabilizers. See for example, U.S. Pat. Nos. 3,413,045, 3,897,837; 4,020,910; 4,013,325; 4,182,425; and 4,262,759. A sealant reservoir for the lubrication of bearings in roller reamers is disclosed in U.S. Pat. Nos. 3,897,837; 4,013,325; 4,182,425; and 4,227,586.
Various sealing means have been provided to seal around the lubricated bearings. U.S. Pat. Nos. 3,897,837; 4,020,910; and 4,262,759 disclose a seal between the roller and the upper end of the shaft. U.S. Pat. Nos. 3,897,837; 4,182,425; and 4,227,586 utilize a seal between the shaft and the block. U.S. Pat. Nos. 4,013,325; 4,020,910; and 4,262,759 disclose a seal between the shaft and cutter. U.S. Pat. Nos. 3,897,837; 4,013,325; 4,020,910; 4,182,425; and 4,262,759 disclose a seal between the roller and the lower end of the shaft.
O-ring seals may be used to seal between the shaft and block as in U.S. Pat. Nos. 3,897,837 and 4,227,586 and to seal between the shaft and roller as shown in U.S. Pat. Nos. 4,013,325; 4,020,910; and 4,262,759. The weld between the upper end of the shaft and the block in U.S. Pat. No. 4,182,425 provides for sealing therebetween.
Two types of seals, namely radial seals and facing seals, may be provided to control the lubricant flow, to prevent loss of lubricant, and to exclude solids and debris from reaching the bearings of the rollers. Radial seals which sealingly engage the inner diameter of the roller and the outer diameter of the shaft are shown in U.S. Pat. Nos. 3,897,837; 4,013,325; 4,020,910; and 4,262,759. The seals are housed in grooves in the roller in U.S. Pat. Nos. 4,020,910 and 4,262,759 and in the grooves in the shaft in U.S. Pat. Nos. 3,897,837 and 4,262,759. In U.S. Pat. No. 4,227,586, the roller is not rotatably mounted on a shaft but includes male bearing journals at each end of the roller. The bearing journals are rotatably received within cylindrical bearing surfaces within bearing blocks. Seals are provided in grooves in the blocks for sealing between the shaft and block. U.S. Pat. No. 4,020,910 discloses a carrier housed in a groove in the roller with the carrier including both a radial seal, sealing between the carrier and shaft, and a facing seal, sealing between the carrier and a retainer on the roller.
A principal disadvantage of radial seals between the shaft and roller is that gravity causes the detritus to work down between the radial seal, shaft and roller to erode and deteriorate the radial seal.
U.S. Pat. No. 4,182,425 in FIG. 9 discloses a triple pressure balanced O-ring sealing at three places, i.e., around the shaft, around the flat top surface of the roller, and around the flat surface at the bottom of the groove in the block. Thus, the seal seals in the axial direction and radially inwardly. The seal in FIG. 9 is a rotating seal with the upper end of the shaft welded to the block.
In prior art sealed bearing reamers where an upper facing seal sealingly engages a sealing surface in a recessed bore in the upper block, the amount of compression established on the o-ring is critical to the achievement of a satisfactory seal life. This compression is determined by the distance between the sealing surface in the bottom of the groove in the block and the sealing surface on the upper end of the roller. These two sealing surfaces must be accurately positioned to achieve the desired compression on the o-ring which is disposed therebetween. Since the bearing race establishes the position of the roller with respect to the shaft, the distance from the bearing race to the upper seal face on the roller and the distance from the bearing race to the bottom of the groove in the block is critical. Where the upper end of the shaft is welded to the block, thereby positioning the sealing face on the block with respect to the sealing face on the roller, the specified distance for achieving the critical compression of the o-ring has been difficult to achieve in a production environment. It has proven difficult to position the shaft within the block and at the same time weld the shaft to the block to achieve the desired distance and therefore the desired compression of the o-ring.
Further, prior art designs require that the annular region between the internal diameter of the block and the outer diameter of the shaft be sealed. This is often accomplished by a weld between the block and shaft. This requires a relatively high-quality pressure-type weld, and results in the upper block becoming an integral part of the roller assembly.
Where the shaft has a bearing area for the rotation of the roller thereon, the shaft is carburized. If the shaft is welded to the block, it is necessary to mask the welding area of the shaft because of the carburization. The shaft is masked by leaving an enlarged end where the shaft will be welded and then the enlarged end is removed prior to welding. By eliminating the need to weld the shaft to the block, these steps are no longer necessary and the weld recess on the shaft is eliminated.
Further, welding the shaft to the block hinders the reuse of the upper block.
It is an object of the present invention to provide a roller reamer with improved sealing means between the roller and shaft thereby enhancing the life of the bearings. The present invention eliminates the need for welding between the block and shaft to position the upper sealing surface or to provide a seal between the shaft and block, and yet still provides the more desirable facing seals. Thus, the present invention provides an improved sealing means to control the lubricant flow, and to prevent loss of lubricant, and to exclude solids.
Other objects and advantages of the invention will appear hereinafter.